Evidence suggests that aging is accompanied by significant changes in the immune apparatus that contribute to the initiation and progression of geriatric diseases. However, the fundamental mechanism underlying immune dysfunction in senescence remains to be fully defined. The objective of this study is to understand the basis of immune dysfunction by focusing on the role of regulatory ubiquitination in human peripheral blood T lymphocytes during aging. The long-term goal of this study is to fully define the molecular basis of immune dysregulation that accompanies aging. Our working hypothesis is that alterations in the regulation of ubiquitination and/or deubiquitination of important signaling intermediaries contribute to T cell dysfunction in the elderly by modulating activation-induced signaling. Our preliminary results demonstrate that (1) there is significant accumulation of ubiquitinated proteins in T cells from the elderly, (2) the induction and activity of transcription factor NFkB, a paradigm for regulatory ubiquitination, is significantly compromised in activated T cells from the elderly, (3) proteasomal-degradation of ubiquitinated proteins is compromised in T cells from the elderly as compared to those from young donors and finally, (4) both ubiquitin conjugating and deubiquitinating activity are significantly altered in T cells from the elderly. With ubiquitination and ubiquitin-like protein modifications taking center stage in processes ranging from induction of trancription factor, to regulation of gene expression, it is likely that aberrant ubiquitination or regulation of ubiquitination may contribute to immune dysfunction in the elderly. Therefore, to understand the basis for this age-related alteration in regulatory ubiquitination, using signaling leading to the induction of NFkappa B as a paradigm, we will specifically : (i) identify and characterize the effect of age on ubiquitination of substrates in T cell subsets, (ii) delineate the underlying mechanism/s for altered ubiquitination in T cell subsets from the elderly and (iii) determine the regulatory role of the proteasome in altered ubiquitination and its functional impact on T cell responses. Results from these studies will provide valuable insights into regulatory ubiquitination in immune function underlying immune senescence in humans and may provide a molecular framework for designing potential therapeutic intervention in not only boosting vaccine efficiency in the elderly but also provide an insight into the role of ubiquitination in geriatric diseases.